Save as problem - pls help

I have some files path store in a string[] variable. I want open each file and send string to execute, like as draw a line in drawing. Then save, close drawing and continue to another file. This is my code:

        [CommandMethod("send")]

        public static void test()

        {

            string Command = "(Command \".Line\" '(0 0) '(0 10) \"\") ";

            string[] Files = new string[3];

            Files[0] = "C:\\test1.dwg";

            Files[1] = "C:\\test2.dwg";

            Files[2] = "C:\\test3.dwg";

            foreach (string fil in Files)

            {

                if (System.IO.File.Exists(fil) == true)

                {

                    DocumentCollection acDocMgr = Application.DocumentManager;

                    Document acDoc = acDocMgr.MdiActiveDocument;

                    try

                    {

                        acDoc = acDocMgr.Open(fil, false);

                        using (DocumentLock DcLck = acDoc.LockDocument())

                        {

                            using (Transaction acTrans = acDoc.Database.TransactionManager.StartTransaction())

                            {

                                acDoc.SendStringToExecute(Command, true, false, false);

                                acDoc.Database.SaveAs(acDoc.Name, true, DwgVersion.Current, acDoc.Database.SecurityParameters);

                                acTrans.Commit();

                            }

                        }

                        acDoc.CloseAndSave(fil);

                    }

                    catch (Autodesk.AutoCAD.Runtime.Exception ex)

                    {

                        acDoc.Editor.WriteMessage("Error: " + ex.ToString());

                    }

                }

            }

        }

But it had error at Save as line. Please help!